Conventional radio frequency devices and microwave devices that are being produced using GaN-on-silicon technology exhibit degraded power added efficiency at frequencies above 1 gigahertz. For example, a GaN-on-SiC based radio frequency power transistor routinely demonstrates a greater than 70% power added efficiency, while a similar GaN-on-silicon high-electron mobility transistor device can only produce a power added efficiency of approximately 60%. The source of the degraded radio frequency performance is a result of a capacitive coupling through undoped AlGaN buffering/transition layers to a conductive parasitic doped layer at a surface of the silicon substrate formed during an epitaxial growth. The capacitive coupling and parasitic conduction layer form an RC network in parallel with the active and passive device structures that provide a path to shunt and disperse charge around the active circuitry rather than deliver the charge to the radio frequency output/load.
It would be desirable to implement a performance enhancement of an active device through reducing parasitic conduction.